Preparation of tropones



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3,084,194 Patented Apr. 2, 1963 3,084,194 PREPARATION OF TRGPGNES Arne P. ter Eerg, Robert van Helden, and Geertruida M. La Roij, ail of Amsterdam, Netherlands, assignors to Shell Gil Qompany, New York, N.Y., a corporation of Deiaware No Drawing. Filed June 8, 1960, Ser. No. 34,619 Ciaims priority, application Netherlands July 2! E59 2 Claims. (Cl. 260-586) It has now been found that tuted In this equation, X represents an oxygen or sulfur atom and R is a monovalent organic radical. In selecting a suitable ether starting material, it is preferred that ethers are chosen in which R no more than 12 carbon atoms.

It will be obvious to those skilled in the art that any desired tropone or thiotropone maybe obtained by selecting the appropriate starting material. Thus, to prepare any given substituted tropone, it is only necessary to start with a tropylether having its tropyl-ring substituted with the substituent desired on the tropone product.

An illustrative group of suitable starting materials and the tropone or thiotropone obtained is as follows:

Tropyl methyl ethertropone Tropyl phenyl ethertropone Tropyl Z-methylphenyl ethertropone Tropyl fi-phenylethyl ether-e tropone Tropyl cyclohexyl ether tropone Tropyl allyl ethertropone 2,3,5-trimethyltropyl methyl ether 2,3,5-trimethyl tropone 3-phenyltropyl ethyl ether) 3aphenyl tropone S-phenylmethyltropyl phenyl ether- 5-phenylmethyl tropone Y Di(2-methyltropyl) ether- Z-methyltropone Di(2-phenyl-3,4-dimethyltropyl) ether 2-phenyl-3,4-dimethyl tropone Tropyl methyl thioether-e thiotropone Tropyl 2-methylphenyl thioether thiotropone Tropyl cyclohexyl thioether thiotropone 2,3,5-trimethyltropyl methyl thioether 2,3,5-trimethyl thiotropone S-phenylmethyltropyl phenyl thioether 5-phenylmethyl thiotropone Di(ZsphenyI-S,4-dimethyltropyl) thioether 2-pheny1-3,4-

dimethyl thiotropone The tropyl ethers as starting materials to be used in this invention maybe obtained by hydrolysis or alcoholysis of the corresponding tropylium salt. The thioether is obtained from the tropylium salt by conversion with hydrogen suufide or a thiol. Assymetrical ethers and thio ethers are obtained by reacting the relevant tropylium Particularly advantageous starting materials are the symmetrical ethers. As seen from the equation illustrating the reaction of this to an ether suitable as a starting material in Simiiarly, symmetrical thioethers yield hydrocarbons suitable for recycling.

The temperature at ether employed as starting material, Whether or not any gas stream is used during heating, and the presence of any diluents, acids, or the like. The operating temperature for the thermal cleavage is generally not above 250 0, although higher temperatures may also be used. Temperatures not exceeding 150 C. and preferably in the range from about 60 C. to about 130 C. are particularly suitable.

The reaction may be very suitably carried out at atmospheric pressure. To prevent undesirable decompositions and side reactions, it has, however, been found advantageous to operate at reduced pressure to permit the use of lower temperatures. Pressures below 200 mm. Hg have been found particularly advantageous.

it has been found to be very advantageous to effect the more of the reaction mixture, it is preferred to use from about 1% to about 5% by weight of the acid selected. Any strong acid (pH 5) is suitable for this purpose. Organic acids such as the acids and sulfonic trichloracetic acid, and the like.

inert solv'ent or diluent.

tane, octane, and tlielike "trated bythe' following examples.

--a, gas supply tube, aimixture of 83 g.

(hf-365;" C.,cycl oheptatriene began to distill ofi.

Strong mineral acids such-as-hydrochloric acid, .sulfuricacid, and-phosphoric acid are very suitable for this punpose. Acidic ion exchange resins are equallysuitable and are preferred. Silica gel has-been foundbtobe particularly well suited tor thispurpose.

The reaction is preferably ether to the eleaya-getemperature mliquid phase while '-astream-off inert gas is passed through at. reduced .pressure, the byproducts dist of inert gas is not essential and it is .alsopossible to carry out the processi-byheating the .appropriate'etherjin vapor phase. If desired, the reactionirnay. be carried out inan Hydrocarbons such toluene, ethylbenzene, hexane, cyclohexaue, hepare suitable solvents.

this invention are best illus- It is to be understood that they are ofiered for illustration only. and are not to be COHSlLl'llfidrElS limiting the invention in any way.

benzene, xylene,

Details of the process of Example I '-In, a'-disti llation apparatus 33.43' g. ofditropyl ether were'he'ated to 115 0-130 C. tor one hour under a vacuun'rof 120 Hg, 7.74- g. of 'cycloheptatriene distilling o t; 'n f- =1:5225; Hence the cycloheptatriene yield was 50%.

The residue 'was then subjected'to a vacuum distillation.

9.25 g. of tropone was obtained boiling at 70 C. at 0.3 nirnJHg; n j =l.6180. Hence'the tropone yield was 50%;

Example II 4 The residue was subsequently subjected to a distillation. 35,'g..ottropone.wflhaboilingpointof C. at 0.3 mm. Hg were obtained. Hence the tropone yield was 78% We claim as our invention:

1 A process for the production of tropones which comprises thermally cleaving jatia. temperature of from about 60 C. to about C. a compound represented by the formula:

wherein (a) 'Xis oxygen,

(5) each of the six R selected' from'thegroup consisting of hydrogen, alkyl' and aryl' radicals-with 'no' more than 10 carbon atoms,

(c) R is ainionovalent hydrocarbon 'group with no more than '12 carbonatornsselectedironi the group consistingof:

(l) the. group:

wherein R is as defined in (b) (2) alkyl, vl (4) alkenyl, and e (-5) cycloalkyL,

2. Aiprocess for-thepreparation oftropone which: comprises heating ditropyl. ether. at a temperature of from about 60 C. to about-130 G.'-at aipressure-below one atmosphere.

References Gitedinthe file of this-patent Docring et;al.: I. Am. Chem; Soc, vol79,,pages 352-6 (.1957 

1. A PROCESS FOR THE PRODUCTION OF TROPONES WHICH COMPRISES THERMALLY CLEAVING AT A TEMPERATURE OF FROM ABOUT 60*C. TO ABOUT 130*C. A COMPOUND REPRESENTED BY THE FORMULA: 